There is no chapters per se, it's open world spanning many locations. I am a completionist in general and explore every nook and cranny...the game took me over 100 hours playing it that way but the length of the game would obviously be much shorter if did not bother doing anything except main quest line and limited your exploration to only places that quest line asked you to go.
There is at least...
four (Cyseal, Luculla, Hiberhiem and Phantom Forest)
...major zones on par or near enough scale wise with Cyseal not including all the caves, temples etc.
